This invention pertains to a syringe or the like for injecting or withdrawing a fluid into or from a patient, and more particularly to a needle retraction system for disarming such a device after use.
The hazards associated with accidental needle sticks are well known. Many issued patents disclose syringes or the like having mechanisms for retracting or otherwise enclosing a syringe needle after use, to prevent accidental contact with the needle.
It is an object of the present invention to provide an improved needle retraction mechanism for use with a syringe or the like for preventing accidental needle sticks. It is a further object of the invention to provide a needle retraction mechanism which is relatively simple in its construction and operation.
In accordance with one aspect of the invention, a syringe assembly includes a barrel having an internal cavity and defining a first closed end and a second open end. A plunger is mounted for longitudinal sliding movement within the barrel cavity. The plunger includes a longitudinal internal passageway. A first end of the plunger is disposed within the barrel cavity, and a second end of the plunger is disposed exteriorly of the barrel. The internal passageway opens onto the first end of the plunger. A retraction member is releasably engaged with the plunger, and is located within the internal passageway at the first end of the plunger. Bias means is provided for urging the retraction member into the passageway toward the second end of the plunger. In one form, the bias means consists of a spring interconnected between the retraction member and the plunger. A needle assembly consists of a needle engageable with a hub member, with the hub member including a passage establishing communication between the barrel cavity and the needle lumen. The needle is selectively engageable with the hub member such that the needle is engaged just prior to use of the syringe assembly. This enables the operator of the syringe assembly to select the appropriately sized needle according to the application in which the syringe assembly is used. In one form, the needle includes a head having external threads engageable with internal threads formed in the passage of the hub member. This enables the operator to remove the needle, if already in place, and replace it with a different needle if desired. In another form, the needle head includes a frustoconical cam surface defining a shoulder, and the hub passage is shaped so as to receive the frustoconical head of the needle. The hub member further includes resilient fingers having hooks at their forward ends, and the fingers are forced outwardly during insertion of the head into the needle passage. The fingers return to their original position to engage the shoulder defined by the needle head after placement of the needle head into the passage, so as to engage the needle with the hub member. In this arrangement, the needle cannot be selectively removed from the hub member after connection thereto.
In accordance with another aspect of the invention, engagement means may be interposed between the retraction member and the hub member for engaging the retraction member with the hub member upon movement of the plunger toward the first end of the barrel. A selectively actuable release mechanism maintains the retraction member in position within the plunger passageway at the first end of the plunger against the force of the bias means prior to engagement of the retraction member with the hub member during movement of the plunger toward the first end of the barrel. The release mechanism functions to release engagement of the retraction member with the plunger after engagement of the retraction member with the hub member. A releasable retainer mechanism is interposed between the hub member and the barrel for releasably engaging the hub member with the barrel. The releasable retainer mechanism is operable to release engagement between the barrel and the hub member, either before or after engagement of the retraction member with the hub member, to provide withdrawal of the hub member and needle into the passageway of the plunger after use of the syringe.
In accordance with yet another aspect of the invention, the plunger longitudinal internal passageway may be defined by a sleeve engaged with the closed end of the barrel. The sleeve includes a first end engaged with the closed end of the barrel and a second end spaced therefrom, preferably extending outwardly of the open end of the barrel. The hub member is disposed within the sleeve adjacent its first end, and bias means, such as in the form of a spring, is interposed between the hub member and the sleeve for biasing the hub member toward the second end of the sleeve. A releasable retainer mechanism is interposed between the hub member and the sleeve. The releasable retainer mechanism is movable between an engaged position in which the hub member is maintained in a fixed position adjacent the first end of the sleeve, and a disengaged release position. An actuator member is interconnected with the releasable retainer mechanism for selectively moving the releasable retainer mechanism to its release position in response to actuation by the operator to provide withdrawal of the hub member, and thereby the needle, into the sleeve to disarm the syringe assembly when desired. The actuator is located adjacent the open end of the barrel, and is engageable by the operator's thumb or finger so as to provide movement of the releasable retainer mechanism to its release position at any time during movement of the plunger. This enables the operator to disarm the syringe assembly whether or not all of the fluid has been ejected from the barrel. Once the hub member is moved to the second end of the sleeve by operation of the bias means, the bias means maintains the hub member in position therein to prevent subsequent reuse of the syringe assembly. Preferably, a one-way stop is provided in the sleeve to engage the hub member to prevent it from moving toward the first end of the sleeve after the hub member has passed by the stop member during disarming of the syringe assembly.
In accordance with further aspects of the invention, the hub member may be received within a sleeve which is engageable with the exterior of the barrel for engaging the hub member with the first end of the barrel. Further, the releasable retainer mechanism may be actuated automatically in response to movement of the plunger. In this form of the invention, the releasable retainer mechanism may take the form of a base disposed between the sleeve and the first end of the barrel, mounted to the barrel by engagement of the sleeve with the barrel. A series of flexible retaining fingers extend from the base and releasably engage the hub member. Movement of the plunger toward the first end of the barrel engages the retraction member with the fingers, which functions to flex the fingers outwardly to release engagement of the hub member with the barrel. Alternatively, the releasable retainer mechanism may take the form of a manually operated actuator member engaged between the barrel and the hub member, to retract the needle after use upon manual actuation by the user. The manually operated actuator member is movable between a retaining position and a release position, and functions to retain the hub member in position relative to the barrel when in its retaining position against the force of the biasing means when the retraction member is engaged with the hub member, and to release engagement of the hub member with the barrel when in its release position to allow the bias means to withdraw the retraction member, the hub member and the needle into the passageway. The first closed end of the barrel terminates in one or more walls defining a restricted passage within which the hub member is disposed when engaged with the barrel. The manually operated actuator member is engaged with the hub member, and is movably mounted to the one or more walls defining the restricted passage between its retaining position and its release position.
In either the manual or automatic versions summarized above, the bias means may take the form of a spring, as noted previously, or alternatively may be in the form of a vacuum provided in the passageway for urging the retraction member toward the second end of the passageway.
The selectively actuable release mechanism may be in the form of peripheral ridge structure provided on the retraction member, and a retaining ring interposed between the peripheral ridge structure and a peripheral end wall defined by the passageway at the first end of the plunger. Movement of the plunger toward the first end of the barrel results in the peripheral end wall forcing the retaining ring over the peripheral ridge structure, to release engagement of the retainer member with the plunger. In this manner, the retraction member functions to withdraw the hub member into the internal passageway defined by the plunger under the influence of the biasing means after the releasable retainer mechanism is operated to release engagement between the barrel and the hub member.
The invention further contemplates a method of disarming a syringe after use, substantially in accordance with the foregoing summary.
Various other features, objects and advantages of the invention will be made apparent from the following description taken together with the drawings.